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Abstract:

A battery electric vehicle charging station is disclosed, having grid and
vehicle connections with a DC charger and controller that selectively
charges the vehicle battery directly with DC power in a first mode and
converts DC power from the vehicle battery to drive an inverter in a
second mode to provide AC power to a power grid.

Claims:

1. A charging station for a plug-in electric vehicle (PEV), comprising:
an inverter including an inverter DC input operative to receive DC input
power and an inverter AC output operative to provide AC output power to
an AC power grid, the inverter being operable to convert the DC input
power to the AC output power; a DC charger, including: a charger DC input
operative to receive power from at least one DC power source, a DC
vehicle battery interface coupleable to a PEV DC battery connection, and,
a DC charger output coupled to the inverter DC input to provide DC output
power to the inverter, the DC charger being operative in a first mode to
provide power from the charger DC input to the vehicle battery interface
and in a second mode to provide power from the vehicle battery interface
to the charger DC output; and, a controller operatively coupled with the
DC charger to selectively switch the DC charger from the first mode to
the second mode.

2. The charging station of claim 1, further including a rectifier, the
rectifier including: a rectifier AC input operative to receive AC power
from the AC power grid; and, a rectifier DC output operative to
selectively convert the AC power to provide DC power to the charger DC
input.

3. The charging station of claim 1, comprising of a photovoltaic
interface coupled with the charger DC input to selectively provide DC
power from a connected solar panel to charge the PEV battery.

4. The charging station of claim 3, wherein the photovoltaic interface is
further coupled to the DC inverter input to selectively provide power
from the solar panel to provide power to the power grid.

5. The charging station of claim 1, the DC charger including a switching
circuit operative in the first mode to electrically couple the charger DC
input to the vehicle battery interface and in the second mode to
electrically couple the vehicle battery interface to the charger DC
output.

6. The charging station of claim 1, wherein the controller is operable to
receive an indicator from an external information source and to
selectively switch the mode of the DC charger between the first and
second modes based at least partially on the indicator.

7. The charging station of claim 6, wherein the external information
source is a user-interface operative to receive a user-command.

8. The charging station of claim 6, wherein the indicator includes a
current price rate for AC power supplied to the AC power grid, where the
controller selectively switches the charger to the second mode if the
price rate is greater than a threshold.

9. The charging station of claim 6, wherein the indicator includes a grid
status, where the controller selectively switches the charger to the
second mode if the grid status is unstable.

10. The charging station of claim 6, wherein the indicator includes an
amount of renewable energy generation on the grid, where the controller
selectively switches the charger to the first mode if the amount of
renewable energy generation on the grid exceeds a predetermined
threshold.

11. A method for operating a plug-in electric vehicle (PEV) charging
system, comprising: selectively operating a DC charger in a first mode,
including: directing DC current from a DC power source through a DC
charger input to the DC charger, and directing DC current from the DC
charger through a DC vehicle battery interface to a vehicle battery; and,
selectively operating the DC charger in a second mode, including:
directing DC current from the vehicle battery through the DC vehicle
battery interface and through a DC charger to an inverter DC input,
converting the DC current to AC current using an inverter, and directing
AC current from the inverter through an inverter AC output to an AC power
grid.

12. The method of claim 11, further including selectively operating a
switching circuit in the second mode to electrically couple the charger
DC input to the DC vehicle battery interface and in the first mode to
electrically couple the DC vehicle battery interface to the charger DC
output.

13. The method of claim 11, further including selectively operating the
switching circuit based on a received indicator.

14. The method of claim 11, further including directing DC current from a
solar panel through a photovoltaic interface and through a DC charger
input to the DC charger in the first mode.

15. The method of claim 11, further including selectively operating the
DC charger in a third mode, including: converting AC current from the AC
power grid using a rectifier and charging the vehicle battery using DC
current from the rectifier.

16. The method of claim 11, further including in a fourth mode, if no PEV
is connected to the DC vehicle battery interface: directing DC current
from a solar panel to the inverter DC input; converting the DC current to
AC current at the inverter; and, directing the AC current from the
inverter using the inverter to the AC power grid.

17. The method of claim 11, further including: making a determination as
to whether a received indicator satisfies an operational condition; and,
selectively entering the second mode based on the determination.

18. The method of claim 17, wherein the operational condition is a
user-command input at an interface.

19. The method of claim 17, wherein the operational condition is a
preprogrammed threshold based on a status of the AC power grid.

20. The method of claim 17, wherein selectively entering the second mode
based on the determination comprises entering the second mode if the
indicator indicates a current price rate for AC power supplied to the
power grid is a preprogrammed threshold.

21. The method of claim 11, including automatically switching to the
second mode at a predetermined time.

22. The method of claim 16, further including: making a determination as
to whether a received indicator includes a quantity of renewable energy
generation on the grid; and, selectively entering the first mode if the
amount of renewable energy generation on the grid exceeds a predetermined
threshold.

Description:

BACKGROUND

[0001] The present disclosure relates generally to a charging station that
can selectively provide DC power to charge a battery based vehicle on a
determined mode of operation. Because battery electric vehicles (BEVs)
and plug-in hybrid vehicles (PHEVs) (collectively called Plug-In Vehicles
(PEVs)) have only recently been introduced in mainstream market channels,
electric vehicle charging infrastructure is limited in the United States
and elsewhere. Hybrid electric vehicles (HEVs), including PHEVs, include
hybrid technology allowing the vehicle to operate using fossil-fuel for
propulsion and battery charging, and some electric vehicle designs
provide an on-board internal combustion engine dedicated to driving a
generator to charge the vehicle battery. If on-board propulsion or
charging facilities are depleted or unavailable and the vehicle battery
presently has a low state of charge (SOC) for the electric propulsion
system, the vehicle must be brought to a charging station before the
battery is completely depleted.

[0002] A typical charging system includes a station operatively coupled to
an AC power source. The PEV generally includes an AC charger that can
receive AC power from an AC power source. However, the PEV operates on
direct current (DC) power from an on-board vehicle battery, and AC
chargers must convert AC power to DC power via internal rectifier
circuitry to charge the vehicle battery, and this conversion creates an
undesirable loss of energy. Thus, there is a need for improved PEV
charging systems and techniques by which charging inefficiencies can be
reduced while providing flexibility in charging options.

SUMMARY

[0003] Various details of the present disclosure are hereinafter
summarized to facilitate a basic understanding, where this summary is not
an extensive overview of the disclosure, and is intended neither to
identify certain elements of the disclosure, nor to delineate the scope
thereof. Rather, the primary purpose of this summary is to present some
concepts of the disclosure in a simplified form prior to the more
detailed description that is presented hereinafter.

[0004] Some charging systems include a charging station capable of
receiving power from multiple power sources, including grid power from a
utility as well as solar panels and/or other alternative power sources.
The charging station provides power to the PEV battery in certain
operating modes, and may employ such alternative sources, for example,
when a primary AC power source cannot provide sufficient power. However,
instances are contemplated in which the vehicle battery becomes fully
charged, and an amount of DC power stored by the vehicle battery may
surpass the needs of the driver. Therefore, it may be desirable to draw
DC power from the surplus vehicle battery charge for other uses. With the
current spotlight being on energy efficiency and clean energy sources, it
may be desirable to partially discharge the vehicle battery and provide
the surplus charge to the power grid. The present disclosure provides a
charging station that can operate as an alternate AC power provider to
support grid power needs while allowing direct DC charging of a vehicle
battery.

[0005] A PEV charging station and PEV charging method are disclosed in
which various modes of operation are selected for providing DC power to
and from a battery electric vehicle. These concepts may be advantageously
employed to facilitate travel using DC power stored in the vehicle
battery, while also selectively providing power to the grid using surplus
power stored in the battery, thus increasing energy efficiency and
potentially providing savings to the user.

[0006] A charging station is disclosed, having a DC charger and an
inverter operatively coupled to a controller. The inverter includes a DC
input operative to receive DC input power and is operative to convert DC
input power to drive an inverter AC output to provide AC output power to
the AC power grid. The DC charger includes a DC input that is operative
to receive power from at least one DC power source, such as a local
storage battery, a solar panel, a rectifier driven from grid power, etc.
The DC charger further includes a DC vehicle battery interface that is
coupleable to a PEV DC battery connection for direct DC charging and for
selectively drawing power from the vehicle battery. The DC charger also
includes a DC charger output coupleable to a DC inverter input to provide
DC power to the inverter. The DC charger is operative in a first mode to
provide power from the charger DC input to the vehicle battery interface.
In a second mode, the DC charger provides power from the vehicle battery
interface to the charger DC output. The controller is operatively coupled
with the DC charger to selectively switch the DC charger from the first
mode to the second mode.

[0007] In certain embodiments, the controller receives an indicator from
an external information source and selectively switches the DC charger
mode between the first and second modes based at least partially on the
indicator. The indicator, for example, may include a current price rate
for AC power provided to the AC power grid, and the controller
selectively switches the charger to the second mode if the price rate is
greater than a threshold. In another embodiment, the indicator may
include a grid status, and the controller selectively switches the DC
charger to the second mode if the grid status is unstable. In another
embodiment, the indicator may include the presence of significant
quantities of renewable generation on the grid (such as wind generation
at night), and the controller selectively switches the DC charger to the
first mode to maximize the use of renewable electricity. The external
information source may be a user interface operative to receive a
user-command for switching the DC charger mode. The controller may thus
facilitate intelligent and/or user-driven switching to provide grid power
derived from excess energy stored in the vehicle battery.

[0008] A method is provided for operating a PEV charging station,
including selectively operating a PEV battery charging system in one of
two modes. In the first mode, DC current is directed from a DC power
source through a DC vehicle battery interface to a vehicle battery. In
the second mode, DC current is directed from the vehicle battery through
the DC vehicle battery interface and through the DC charger to an
inverter DC input. The DC current is then converted to AC current using
an AC inverter and the AC current is directed through an inverter AC
output to an AC power grid.

[0009] Certain embodiments include selectively operating the DC charger in
a third mode in which AC current from the grid is converted using a
rectifier and DC current from the rectifier is used to charge the vehicle
battery. In certain embodiments, moreover, the charging system is
operated in a fourth mode if no PEV is connected to the DC vehicle
battery interface, in which DC current is directed from a solar panel
through the inverter DC input for directing AC current to the AC power
grid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The following description and drawings set forth certain
illustrative implementations of the disclosure in detail, which are
indicative of several exemplary ways in which the various principles of
the disclosure may be carried out. The illustrated examples, however, are
not exhaustive of the many possible embodiments of the disclosure. Other
objects, advantages and novel features of the disclosure will be set
forth in the following detailed description of the disclosure when
considered in conjunction with the drawings, in which:

[0011]FIG. 1 is a schematic diagram illustrating a charging system
according to various aspects of the disclosure;

[0012]FIG. 2 is a partial schematic diagram illustrating a charging
station showing an operating scheme for multiple modes of operation
according to various aspects of the disclosure;

[0013]FIG. 3 illustrates an exemplary plug-in vehicle (PEV) having a
vehicle DC input for receiving DC power in accordance to various aspects
of the disclosure; and,

[0014]FIG. 4 is a flow diagram illustrating an exemplary mode selection
process for a PEV charging station according to various aspects of the
disclosure.

DETAILED DESCRIPTION

[0015] One or more embodiments or implementations are hereinafter
described in conjunction with the drawings, where like reference numerals
are used to refer to like elements throughout, and where the various
features are not necessarily drawn to scale. The disclosure relates to
plug-in vehicles (PEVs), and to a charging station that uses various
operation modes to charge PEVs using DC power. The disclosure more
particularly relates to a PEV charging station and charging method that
provides power to the PEV in a first mode and provides power to an energy
source in a second mode, for instance, when the state of charge (SOC) of
the PEV battery exceeds a need or surplus.

[0016] Referring initially to FIG. 3, an exemplary plug-in vehicle (PEV)
100 is illustrated having a vehicle DC input 360 for receiving and
providing DC power from or to a charging station in accordance with one
or more aspects of the disclosure. The PEV 100 includes a propulsion
system 301 having an electric motor 314 with a shaft 302, a front wheel
drive axle 306 and a differential gear 304 for propelling the vehicle 100
via wheels 308. The propulsion system 301 further includes a battery 310
providing DC current to a vehicle 312, which in turn provides AC current
to the motor 314 coupled by output shaft 302 with the axle 306 via the
differential gear 304. The electric motor 314 drives the shaft 302 to
transfer motive power to the differential gear 304, which transmits the
motive power to the front wheels 308 by the axle 306 to propel the
vehicle 100. One or more additional gears (not shown) may be included.

[0017] The battery 310 can be any suitable single or multiple battery
configuration to supply DC power to the motor 314, for example, a nickel
metal hydride, lithium ion, or similar battery, and DC-DC boost circuitry
such as a DC-DC converter (not shown) may be included to adjust the DC
output of the battery 310 to any level suitable for providing an input to
the inverter 312. The inverter 312 receives the DC power directly or
indirectly from the battery 310 and converts it to AC power to control
the drive motor 314 to drive front wheels 308. The drive system may
include one or more alternative charging means for charging the battery
310, for example, where the motor 314 may operate as a generator during
vehicle braking to convert rotational energy from the wheels 308 into
electrical energy, with the inverter 312 or other circuitry converting
such power to DC current to charge the battery 310. In addition, the
vehicle battery 310 may be charged using an on-board AC-DC charger 362
from an externally supplied AC source coupled to an AC input 364 or the
battery 310 in this example can be directly charged from an external DC
source (such as the exemplary charging station of FIG. 1) using a direct
DC charging input 362 as described in greater detail below.

[0018] A propulsion controller 320 in the vehicle 100 controls the
inverter 312 according to driver inputs from sensors (not shown)
associated with the vehicle 100. The propulsion controller 320 can be
implemented as any suitable hardware, processor-executed software,
processor-executed firmware, programmable logic, or combinations thereof,
operative as any suitable controller or regulator by which the motor 314
and/or the inverter 312 can be controlled according to one or more
desired operating values such as speed setpoint(s). The controller 320
obtains a state of charge (SOC) signal or value from the battery 310 or
from a controller associated therewith (not shown). The propulsion
control unit 320 in certain embodiments calculates an output that the
driver requests and determines the vehicle speed from an output signal or
provided value. From these, the propulsion controller 320 determines a
required driving power for controlling the inverter 312 and thus the
motor 314, where the inverter control can include one or both of speed
control and/or torque control, as well as other motor control techniques.

[0019] The vehicle 100 further includes an on-board navigation system 350,
which can be implemented as a processor-based computing device with
corresponding programming instructions. The navigation system 350
communicates with the propulsion controller 320 and also directly or
indirectly communicates with a charging station (e.g., FIG. 1) when
coupled with the DC input 360, for example, to provide an expected
driving distance of a route programmed into the system 350 by a user, or
to provide a corresponding expected SOC value required to drive the
vehicle 100 on a programmed route stored in the navigation system 350.

[0020] With continued reference to FIG. 3, an on-board AC/DC charger 362
is provided. A vehicle AC input 364 receives AC current from an AC power
source to charge the vehicle battery 310. In a typical charge operation,
the vehicle AC input 364 is coupled to the AC power source using an AC
power source connection, and the on-board AC/DC charger 362 converts the
AC power to DC power. The AC/DC charger 362 provides DC power to the
vehicle battery 310. One advantage of the vehicle DC input 360 provided
on the PEV 100 is an ability to supply DC power to the motor 314 directly
from a DC power source without the inefficiency inherent in an AC-DC
conversion required when instead using the on-board AC-DC charger 362.

[0021]FIG. 1 illustrates an exemplary charging system 10 (hereinafter
synonymously referred to as "charging station") with the ability to
selectively use vehicle battery power to supplement an AC power grid
according to one or more aspects of the disclosure. The charging system
10 may be contained in a housing (not shown) adapted for mounting in a
garage or for support in a similar parking facility. The charging system
10 is not limited to home or garage use. Rather, the housing may be
included as part of a kiosk that is mounted to a support unit or on a
support surface that is situated in proximity to a PEV parking spot to
provide a PEV 100 with selective access to the charging system 10. The
housing may include a user input/output interface 12. The interface 12
may communicate with a display for displaying information to users, and
may further include an input device, such as a keyboard, a microphone, or
a touch or writable screen, for inputting instructions, and/or a cursor
control device, such as a mouse, trackball or the like, for communicating
user input information and command selections to a controller 14. The
interface 12 may include a network interface, which allows the controller
14 to communicate with other devices via a computer network, such as a
local area network (LAN), a wide area network (WAN), or the Internet.

[0022] The controller 14 includes a memory and a processor for processing
instructions stored in the memory to implement the features and functions
described herein as well as other tasks associated with operation of a
charging station. The controller 14 is operable to receive instructions
entered by the user at the interface 12 and/or to receive one or more
indicators provided from an external source by a communication interface
16. Instructions stored in the memory of the controller 14 include a mode
determination component directed toward selectively providing DC or AC
power based on input received by the various interfaces.

[0023] The charging system 10 is operatively coupled to various power
sources, one of which is a photovoltaic source 20 (hereinafter referred
to as solar panel). The solar panel 20 may include multiple panels
operable to generate electrical power by converting solar radiation
emitted from the sun 22 into direct current electricity. The solar panel
20 provides DC power to the charging station 10 via a photovoltaic
interface 24. It is anticipated that the solar panel 20 may be included
at or in proximity to the facility containing the charging system 10. A
photovoltaic array may be associated with a building, as either
integrated thereto or mounted thereby, or as a standalone device. The
solar source 20 advantageously provides a green source for PEV battery
charging and may be particularly advantageous where grid power is
expensive. However, the solar panel 20 may not be able to provide
constant DC power in a 24-hour period because of limited daylight hours
for converting energy from the sun 22 into electricity. In particular
seasons, the period of sunlight is also shortened. Furthermore, the needs
of the driver may require that the DC power stored in the vehicle battery
310 is present in an amount that is greater than the solar panel 20 is
able to provide.

[0024] Accordingly, the charging station 10 may be further coupled to an
electrical grid or any electrical network (hereinafter referred to as
power grid 30). The power grid 30 generates, transmits and distributes AC
power from a grid location remote from the charging station 10. The power
grid 30 is operable to provide AC power to the charging station 10
through a power grid interface 32.

[0025] As mentioned, the charging station 10 can provide charging power to
the vehicle battery derived from a number of different sources. There is
no limitation made herein to the number of interfaces provided on the
charging system for coupling the system to power sources. With continued
reference to FIG. 1, another power source for providing power to the
charging station 10 may include a local storage battery 40. The local
storage battery 40 is coupled to the charging station using a battery
connection 44 via an interface 42. In an exemplary embodiment, the local
storage battery 40 stores a surplus supply of DC power, such as power
received from the solar panel 20 when no vehicle battery charging is
underway. This DC power may then be provided to the PEV 100 using the
charging station 10 at a later time. The local battery 40 may provide
this DC power through the battery interface 42. At any time, moreover,
the local charging station 10 can charge the local storage battery 40 to
store excess grid power and/or solar energy output when the PEV 100 is
not connected to the charging station or when otherwise desirable.

[0026]FIG. 1 further illustrates the PEV 100 connected to a DC charger 50
of the charging system 10 through a DC vehicle battery interface 60. The
DC charger 50 is operable to receive DC power at a first voltage from a
first source (e.g., from the solar panel 20, from the local battery 40,
from a rectifier 70, etc.) and to provide the DC power to a second source
(e.g., to the vehicle battery) at a second voltage. The first voltage may
equal or differ from the second voltage, where the charger 50 may include
level conversion circuitry (not shown) to perform any such level
adjustment. A charger DC input 52 is operative to receive the DC power
from the first source. The solar panel 20 is coupled to the photovoltaic
interface 24 of the charging station 10 using a photovoltaic source
connection 26, and the charger DC input 52 receives DC power from the
solar panel 20. The DC charger 50 may alternatively receive input DC
power from the rectifier 70 or from the local storage battery 40, which
is coupled to the battery interface 42 of the charging station 10.

[0027] In a first mode, the DC charger 50 provides the DC power from the
charger DC input 52 to the vehicle battery interface 60 for direct DC
charging of the vehicle battery. The vehicle battery interface is coupled
to the PEV DC battery connection 62, which provides the DC power to the
vehicle DC input included on the PEV 100 (see 360 of FIG. 3). In a second
operating mode, the charger 50 directs DC power from the vehicle battery
to a DC output 54 to drive an inverter 80 to provide AC output power to
the grid 30.

[0028] With continued reference to FIG. 1, a rectifier 70 is another power
source from which the charger DC input 52 is operative to receive DC
power. The rectifier 70 in certain embodiments is integrated into the
charging system 10. The rectifier 70 is operative to selectively convert
AC power from the grid 30 to DC power for use in charging the vehicle
battery and/or the local storage battery 40. Accordingly, the rectifier
70 is coupled to the power grid 30 at the power grid interface 32 and
includes a rectifier AC input 72 that is operative to receive AC power
from the AC power grid 30. A rectifier DC output provides the converted
DC power to the charger DC input 52.

[0029] The controller 14 selectively determines which power source is used
to provide DC power to the input of the DC charger 50. An aspect of the
present disclosure involves use of the PEV vehicle battery 310 as a
suitable power source when a supply of DC power is stored in the vehicle
battery, particularly where the controller 14 can ascertain that the
vehicle state of charge (SOC) exceeds the amount required to traverse a
route programmed into the vehicle navigation system, or where it is
expected that the vehicle battery can be recharged (in whole or in part)
prior to being driven on a selected route, or in other situations, such
as where the current cost of grid power warrants conversion of vehicle
battery charge to supply AC power to the grid 30 or in an unstable grid
condition. For instance, the exemplary charging station 10 is operable to
use the vehicle battery 310 (FIG. 3) as a power source when an amount of
DC power stored in the vehicle battery exceeds needs of the driver, or
when a grid power cost exceeds a threshold, or when a user interface
input requests such a transfer, or when the condition of the grid is
indicated to be unstable.

[0030] In one scenario, a utility company (not shown) generates AC power
and distributes it to one or more grids (e.g., grid 30), by which it is
further provided to consumers. The AC power is provided at a certain rate
(cost), which is typically based on kilowatts consumed in an hour
("kWh"), which may be fixed or variable, and different rates may be
applied for different consumers. In certain regions, the rate is a
computed price based on consumption and demand. Accordingly, a utility
company may selectively lower and/or increase rates based on certain
influxes observed in the market. For example, the rates in certain
regions are lowered during evening hours because there may exist a lower
demand for power. In some instances, the utility company lowers the rate
to encourage consumers to use the energy during off-peak periods. Rates
may be set according to various market clearing houses, such as, for
example, the California Independent System Operator (CAISO) or the PJM
Interconnection (PJM).

[0031] The power grid 30 receives AC power from multiple generation means,
such as, for example, industrial power plants, coal plants, nuclear
plants, hydroelectric plants, and windmills, etc. Moreover, the utility
company is also capable of buying energy from its consumers. The
exemplary charging system 10 is operable to selectively sell to the
utility company a surplus of DC power contained in the vehicle battery
310 by selective operation of the DC charger 50 in a second operational
mode to provide a DC output 54 to power an inverter 80 to generate and
provide AC power to the grid interface 32 by conversion of stored vehicle
battery power.

[0032] With continued reference to FIG. 1, the charging station 10
includes an inverter 80 coupled to the DC charger 50 and the power grid
30. An electrical connection 56 couples the charger DC output 54 to the
inverter DC input 82 for providing DC output power to the inverter 80. In
one embodiment, the inverter DC input 82 is coupled electrically to a
second DC power source, which also provides DC power to the inverter 80.
As is illustrated in FIG. 1, the inverter DC input 82 is coupled to the
photovoltaic interface 24 for receiving DC power provided by the solar
panel 20. The inverter DC input 82 receives DC input power and the
inverter 80 converts the DC input power to AC output power. An inverter
AC output 84 provides AC output power to the AC power grid 30 via the
interface 32. The inverter AC output 84 is represented as including two
lines in FIG. 1, although a multi-phase connection can be used and there
is no limitation made herein to a number of phase lines used for the AC
electrical connections used in the charger station 10.

[0033] As mentioned, the present charging station 10 is operative in a
first mode to provide DC power from the charger DC input 52 to the
vehicle battery interface 60 for charging the vehicle battery using DC
input power received from any of the solar panel 20, the rectifier 70
and/or the local battery 40. The inverter 80 allows the DC charger 50 to
selectively operate in a second mode, wherein the DC charger 50 is
operative to provide DC power from the vehicle battery interface 42 to
the charger DC output 54, thereby allowing provision of auxiliary grid
power using the inverter 80. The controller 14 is operatively coupled
with the DC charger 50 to selectively switch the DC charger 50 from the
first mode to the second mode.

[0034] With reference to FIG. 2, a partial schematic diagram of the
charging station 10 is shown, illustrating further details of the DC
charger 50. The DC charger 50 selectively switches from the first mode to
the second mode using a switch circuit 200. In the first mode, the switch
200 selectively operates in a first position (shown in the figure). More
particularly, the switch 200 in this example includes two contacts 202
and 204 and closes a first circuit 202 formed between the positive
charger DC input 52 (DCIN+) and the corresponding positive
connection of vehicle battery interface 60. The switch simultaneously
closes a second circuit 204 formed between the vehicle battery interface
and the negative charger DC output 54 (DCIN-). The switch 200 thus
connects the DC input 52 with the PEV battery interface 60 so that DC
current may flow from a DC power source 20, 40, 70 to the vehicle battery
310, and no power is provided to the inverter 80 when the DC charger 50
is operating in the first mode. Accordingly, the charging station 10
charges the PEV battery 310 provides DC power to the vehicle battery in
the first mode.

[0035] With continued reference to FIG. 2, the charging station 10 is
operable to receive DC power from the vehicle battery 310 when the DC
charger 50 is operating in the second mode. In the second mode, the
switch 200 selectively operates in a second position with the first
contact 202 connecting DC the positive PEV interface connection to the
positive DC output terminal 54 (DCOUT+) and with contact 204
connecting the negative PEV interface connection to the negative output
54 DCOUT-. In this mode, DC current cannot flow from any of the DC
power sources 20, 40, or 70 to the vehicle battery 310, and instead, DC
output power may be provided from the PEV battery to the inverter DC
input 82, and the DC output power is converted to AC output power for
delivering to the power grid 30.

[0036] The controller 14 may operate other switching circuitry in the DC
charger 50 for other modes of operation in the charging station 10. In
certain embodiments, for example, the switch 200 can have three positions
(not shown) selectable by the controller 14. For example, a third
position may operate to open both the first and second circuit contacts
202, 204, and DC power may be provided by the photovoltaic interface 24
directly to the inverter DC input 82 for providing power to the grid 30.
In this manner, the DC charger 50 may selectively sell power generated by
the solar panel 20 to the AC power grid 30, for instance, when the PEV
100 is not connected to the charging station 10 or otherwise is fully
charged (or charged enough to accommodate any planned trips), or when the
PEV is connected to the AC power grid at a different location. In this
mode of operation, DC current is directed from the solar panel 20 to the
inverter DC input 82, and the DC current is converted to AC current for
the grid 30 using the inverter 80.

[0037] There is no limitation made herein to a number of positions
operable in the switching circuitry of the DC charger 50 or to a number
of switches used for achieving select modes of operation. Furthermore,
embodiments are contemplated to include a switching circuit in one or
more of the inverter 80, the controller 14 and rectifier 70, and certain
embodiments may include diodes (not shown) in the charging station 10 for
maintaining current flow in one select direction.

[0038] The controller 14 can be implemented as any suitable hardware,
processor-executed software, switch driver circuitry, memory equipped
processor-executed firmware, programmable logic, or combinations thereof,
which are operatively coupled to the DC charger 50 to selectively switch
the DC charger 50 from the first mode to the second mode and perform
other switching control functionality for the charger operations
described herein. The controller 14 may send an electrical signal or a
message including control commands or instructions to the DC charger 50
for operating the switching circuit 200 in the first position or the
second position. Generally, the controller 14 provides the mode signal to
the switching circuit 200. The controller 14 may use a smart device or
communicate a message to the switch circuit 200 based on instructions
stored in the previously mentioned memory.

[0039]FIG. 4 is a flow diagram illustrating an exemplary mode selection
process 400 for a PEV charging station according to various aspects of
the disclosure. The PEV connects to the charger station at 402, for
example, using the vehicle battery interface 60 and cable 62 shown in
FIG. 1. The vehicle battery is charged as needed at 410. As mentioned,
the DC photovoltaic or another DC source may direct DC current through
the DC charger to the vehicle battery interface. The operation of
charging the vehicle battery is thus provided in a first mode at 410.
Similarly, the local battery may be charged, as needed, using a DC
source.

[0040] With continued reference to FIG. 4, the controller continues to
operate the DC charger in the first mode until a determination is made to
switch modes at 420, 430. In one embodiment, the controller may be
programmed to switch the operating mode to the second mode at 420. More
particularly, a preprogrammed instruction (e.g., entered by a user via a
user interface 12 or programmed by an external device via a
communications interface 16 in FIG. 1) may direct the controller to
switch the DC charger to operate in the second mode when a select
condition is met. In one embodiment, the condition may set the mode
change to occur at a certain time or during certain times. For example,
the controller may be programmed to switch the mode during daytime hours.
In another embodiment, the controller may be preprogrammed to switch
modes when the vehicle battery becomes full, or when a certain amount of
surplus power is stored in the battery. If such a programmed event occurs
(YES at 420), the process 400 switches to the second mode at 440.

[0041] With continued reference to FIG. 4, if no instruction is
programmed, the controller selectively changes the mode of operation to
the second (battery discharge) mode when an indicator is received at 430.
The indicator can be provided from an external information source. For
example, the external information source may be the utility company,
which sets rates for the purchase of AC power. The indication may be
received as a communication along the grid as a power line communication.
For example, the grid may communicate a carbon dioxide (CO2) content
of grid energy. The external information source may include a vehicle
navigation system 350 (FIG. 3), which can communicate a vehicle battery
state of charge. Furthermore, the navigation system 350 may communicate
an available discharge amount, which is computed using a planned or an
expected charge usage for the next trip. The indicator may alternatively
be provided through the input/output interface. The controller determines
if such an indicator signal or value has been received at 432. If no
indicator is received (NO at 432), the controller continues to operate
the DC charger in the first mode. However, if an indicator is received
(YES at 432), the controller determines the type of indication at
434-438.

[0042] A determination is made at 434 as to whether a use input command
indicator has been received. This indicator may be provided to the
controller using the input/output interface included on the charging
station. Alternatively, the command may be communicated to the controller
from a remote device. The indicator may be provided in real-time for an
immediate switch from the first mode to the second mode. It is
contemplated, for example, that a user may become aware of particular
destinations to which the PEV may be driven and the current charge state
of the vehicle battery is more than what is needed for the planned
trip(s). The user may select to sell excess DC power that is stored in
the DC vehicle battery. The command to switch to the second mode at 440
may be made when the user determines that power required for the
destinations of which the user needs to drive the vehicle is less than
the stored amount. Alternatively, the user may command the controller to
sell AC power to the grid at a select time, and such a command may be
provided in advance of the designated sell time. If such a command
indicator is received (YES at 434), the process proceeds to 440 for
switching to the second mode.

[0043] If no user command indicator is received (NO at 434), the
controller makes a determination at 436 as to whether an indicator signal
representing a current price rate has been received at 436. The current
price rate in certain embodiments can be a price offered by the utility
company for AC power supplied to the AC power grid. At 436, the
controller selectively switches the charger to the second mode at 440 if
the price is greater than a threshold price stored in the memory (YES at
436).

[0044] If the threshold is not met, or no price indicator is received (NO
at 436), the controller determines at 438 whether an indicator signal or
message is received representing the grid status. Many reasons may cause
a power grid to become unstable. For example, a faulted component may
drain power from the power grid, making it less stable. Grid hackers can
make the grid unstable. Transmission lines may be congested, or even
failed. The power grid may also be determined as having an unstable
status when the electricity supply is stressed by over-demand. When power
grid status is unstable, the power grid is in need of an additional AC
power supply. Accordingly, an indicator communicated from an external
power source, such as the power grid, indicates a stability of the grid
status. If the grid status is indicated as stable (NO at 438), the
controller continues to charge the vehicle battery of the connected
vehicle in the first mode 410. However, an unstable grid status (YES at
438) causes the controller to switch the mode of operation to the second
mode at 440.

[0045] With continued reference to FIG. 4, the vehicle battery provides AC
power to the AC power grid at 450 by directing DC current from the
vehicle battery to the inverter and directing AC current from the
inverter to the grid. When the system is operative in the second mode,
certain indicators can be used to further determine when to switch and/or
return the system to the first mode. For example, the system can
determine if there is presence of significant quantities of renewable
generation on the grid at 452. An example of a renewable energy
generation can include wind generation during periods outside of the peak
demand when there is lower consumption of energy, such as during the
night. In this manner, the system operates to maximize the use of
renewable electricity. The system can be programmed with a threshold for
indicating the significant quantity of renewable energy available. One
embodiment can be tailored to any relevant metric by which a relative
amount of renewable energy generation can be addressed or determined. In
addition, the system may obtain the indicator including information
relating to a current level of renewable energy generation from any
suitable source, such as a reporting service, a utility operator, etc.
The system can be programmed in one embodiment to switch the DC charger
to the first mode at 454 when the indicator indicates the presence of a
significant quantity of renewable generation on the grid, for example
where the indicated level exceeds a predetermined threshold amount or
value stored in the system (YES at 452).

[0046] Otherwise (NO at 452), the controller continues an operation of the
DC charger in the second mode until the vehicle battery completes a
discharge at 456. In one embodiment, the battery completes the discharge
when a certain threshold of DC power is discharged from the battery. In
another embodiment, the battery completes the discharge when a certain
threshold of power remains in the battery. For example, the controller
may be programmed to maintain a certain minimum of DC power in the
vehicle battery to provide the PEV with an ability to travel certain
distances, such as those programmed into the vehicle navigation system
350. Once the discharge level is met, the controller switches the DC
charger from the second mode to again operate in the first mode at 410.

[0047] The above examples are merely illustrative of several possible
embodiments of various aspects of the present disclosure, wherein
equivalent alterations and/or modifications will occur to others skilled
in the art upon reading and understanding this specification and the
annexed drawings. In particular regard to the various functions performed
by the above described components (assemblies, devices, systems, and the
like), the terms (including a reference to a "means") used to describe
such components are intended to correspond, unless otherwise indicated,
to any component which performs the specified function of the described
component (i.e., that is functionally equivalent), even though not
structurally equivalent to the disclosed structure which performs the
function in the illustrated implementations of the disclosure. In
addition, although a particular feature of the disclosure may have been
illustrated and/or described with respect to only one of several
implementations, such feature may be combined with one or more other
features of the other implementations as may be desired and advantageous
for any given or particular application. Also, to the extent that the
terms "including", "includes", "having", "has", "with", or variants
thereof are used in the detailed description and/or in the claims, such
terms are intended to be inclusive in a manner similar to the term
"comprising".